Open AccessGraphene aperture-based metalens for dynamic focusing of terahertz waves
Author(s) -
Pei Ding,
Yan Li,
Li Shao,
Ximin Tian,
Junqiao Wang,
Chunzhen Fan
Publication year - 2018
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.028038
Subject(s) - optics , focal length , graphene , terahertz radiation , aperture (computer memory) , cardinal point , lens (geology) , physics , modulation (music) , materials science , acoustics , quantum mechanics
We theoretically study a tunable reflective focusing lens, based on graphene metasurface, which consists of rectangle aperture array. Dynamic control of either the focal intensity or focal length for terahertz circular polarized waves can be achieved by uniformly tuning the graphene Fermi energy. We demonstrate the graphene apertures with the same geometry; however, spatially varying orientations can only control the focal intensity. To change the focal length, the spatially varying aperture lengths are also required. A comparative study between the metalenses, which generate only geometric or both gradient and geometric phase changes, has shown that the apertures' spatially varying length distribution is the key factor for determining the modulation level, rather than the focal length's modulation range. This kind of metalens provides tunable, high-efficiency, broadband, and wide-angle off-axis focusing, thereby offering great application potential in lightweight and integrated terahertz devices.